SEMA4B (Semaphorin 4B): SEMA4B is a gene that encodes an enzyme essential for the biosynthesis of selenoproteins, which contain the amino acid selenocysteine. Predominantly located in the cytoplasm, SEPHS1 plays a key role in selenium metabolism by producing selenophosphate, the activated form of selenium required for selenocysteine incorporation into proteins. Through this activity, SEPHS1 supports the proper synthesis of selenoproteins, which are important for various cellular processes and overall cellular health.